A real beta
You waited for this for a long time, didn't you? You'd been begging him to use you. You'd been aching for him, toddling after him like a puppy after its master. You sucked at his cock and let him fuck your throat until your face was covered in your own spit. You licked his asshole clean while he jerked off. You stripped and bent over when he had friends over so they could admire his property.
Did you really believe him when he said that he might breed you one day? Is that what kept your pussy pulsing when he pushed your head down until you gagged, then kept pushing?
I don't think that was what made you drip down your legs. I don't think that's what kept you awake at night, desperate for release from the ache between your thighs. I think it was the thought of this moment - the moment he bends you over, ass up and cheeks spread, and for a soaring moment you think he'll finally fuck you for real.
But then he tells you that betas aren't for breeding. Betas are for using, and there are only two holes on you that he can use.
It doesn't matter to him that your asshole aches and feels like it might pop when he sodomizes you. The closest thing to vaginal pleasure - the pleasure reserved for real women, not betas - you get to feel is the cold slap of his balls against your ignored pussy. He reminds you that if he catches you touching yourself, you'll regret it, and you believe it. You aren't allowed to touch his property.
And the fucked up thing is that the denial makes you even wetter. Your pussy juices gush out with every thrust in your ass, every moment of deprivation for your aching cunt, and so there's no denying it. That's what a real beta looks like. You're a real beta now.
Don't worry, darling, he'll be done soon. He won't waste his time trying to finish in your ass - that's what your mouth is for!